Studies of mutant alleles in patients and kindred with 21-hydroxylase adrenal hyperplasia has been carried out using allele specific oligonucleotide hybridization and have identified 24 alleles with point mutations, one allele with 2 mutations. However, because of excessive cross hybridization, to improve detection of heterozygous deletions, single strand confirmation polymorphism analysis will be used. Comparison of clinical findings and genotypes will continue.